Holder for mill screens



April 6, 1937. G. c. J. GRAY 2,076,297

HOLDER FOR MILL SCREENS Filed Sept. 18, 1933 Fig.3

gyvuwm G.C.-J. Gray any. M

Patented Apr. 6, 1937 UNITED STATES PATENT OFFICE HOLDER FOR MILL SCREENS Garold C. J. Gray, Hastings, Nebr., assignor to Western Land Roller Company, Hastings,

Paul, N ebr.,

of M. C. An- Anderson, St.

Edna Anderson,

Arthur H. Anderson and Charles M. Anderson, Hastings, Nebr.

Application September 18, 1933, Serial No. 689,971

4 Claims.

My invention relates to means for securing the screen firmly in place in mills, the screen functioning to conduct the ground material from the mill and to retain the unground and partly ground material.

The primary object of the invention is the provision of securing means so designed and arranged that the screen may be replaced in the minimum of time and with the minimum of effort.

Another object of the invention is the provision of fixed arcuate abutments in the mill together with movable clamping elements for pressing the screen against the fixed abutments.

Another object of the invention is the provision of arcuate clamping means pivotally connected with the mill and having a dead center latch.

Having in view these objects and others which will be pointed out in the following description, I will now refer to the drawing, in which Figure 1 is a view in perspective of a mill, parts of the casing being broken away to disclose the screen and the means for holding the screen in position within the mill casing.

Figure 2 is a view partly in side elevation and partly in section showing the screen and the latching elements.

Figure 3 is a View partly in rear elevation and partly in section, showing particularly the eccentric adjusting devices.

In the present instance the mill is a hammermill but the invention is adapted for use in any mill having a screen. The casing includes two side walls It in which is journalled the grinder shaft II. In such mills the ground material is thrown through a screen, the coarser material being retained in the mill for further grinding until it has been reduced to a size such that it will pass through the screen. Particularly in the case of feed grinders, demands are made for grinding the material to various degrees from the coarsest to the finest and it therefore becomes necessary to employ a number of screens which may be used interchangeably. This is true particularly of custom work in grinding feed. The difficulty in most prior mills has been that screens were wedged so tightly in place that it has been diiiicult to remove them, the difficulty being increased by the fact that the new screen must be wedged in the position previously occupied by the screen which has been removed. The work of removing a wedged screen is not only difficult but it requires more time than is available when the work is rushing. It is these difliculties which I eliminate in the use of my screen holder.

The side walls II] of the casing are each provided with a rib I2 extending inwardly from the casing. These ribs are arcuate and concentric with the axis of the shaft II. They are also so positioned as to clear the rotating grinding elements. The screens I3 are also arcuate with the same curvature as that of the ribs I2. It is to be understood of course that the screens I3 all have the same relative outline and they differ from each other only in the size and number of the openings through them. Because of their form their lateral edges will rest naturally against the ribs I2.

The clamp I4 has two parallel curved arms connected at the top by a bar I4. The arms I4 and the bar I 4 are preferably made integral. The curvature of the arms I4 is the same as that of the screen I3 and of the ribs I2. When the parts are latched together they will be in the position shown in full lines in Figure 2. The arms I4 are pivotally secured to a rod I5 the ends of which are anchored in the side walls III. The latching member may thus be moved about the rod I5 as a pivot either toward or away from the screen.

Pivotally secured to the arms I4 and near the upper end thereof is a yoke having arms I6 connected at the outer ends by means of a handle member I 1. Other arms I8 are pivotally connected to the arms I6, the pivotal points being somewhat oiiset, as best shown in Figure l. The arms I8 are secured to a rod I 9 the ends of which are anchored in the side walls III by means to be subsequently described. By grasping the handle I! the arms I6 may be moved into either the full line position or the dotted line position of Figure 2. In the full line position the clamping arms I4 are forced into intimate contact with the screen I3 the edge portions of which are pressed throughout their length against the ribs I2. In the dotted line position the clamping arms I4 are pulled away from the screen so that the screen may be easily withdrawn from the mill. The lower ends of the clamping arms I4 must naturally be so formed with reference to the pivot I5 that it may readily be disengaged when in the dotted line position of Figure 2. The device is further provided with stops 20 for limiting the downward movement of the arms I6 to their screen latching position. It should also be noted that the pivots between the arms I6 and I8 are slightly ofiset so that a dead center latch is provided.

I also provide means for adjusting the pressure exerted by the latching arms I 4 against the screen I3. These means are best shown in Figure 3. The rod I9 is not directly anchored in the walls IE] but it passes through an eccentric 2! at each end of the rod. Each eccentric is frusto-conical in form and it is seated in a tapered aperture in a wall Hi. The rod is screw 5 threaded on one or both of its ends and provided with a nut-or nuts. By loosening the nut or nuts, each eccentric may be turned in its socket so as to either increase or decrease the distance of the rod is from the ribs i2.

The screen is held in place between the ribs l2 and the arms i l but in addition abutments are provided for the opposite end edges of the screen. These abutments function chiefly in the insertion of the screen in the mill. The concave of the mill is corrugated, one of the corrugations being shown at 22 immediately above the floor 23 of the casing. The corrugation 22 limits the movement of the screen when the screen is being inserted in the mill. The top wall 24 of the casing is provided with an opening at 25 for giving access to the screen, to the screen latch and to other interior parts of the mill. The opening 25 is provided with a closure not shown in the present drawing since this closure does not function 25 in connection with the present invention. The opening 25 not only gives access to the interior parts of the mill but it permits the swinging of the arms It in an are through the opening. The corrugation 25 limits the upward sliding movement of the screen which readily snaps in place against the corrugation 25 when the bottom edge of the screen abuts against the corrugation 22. At the same time it is an easy matter when the clamping arms M are in their dotted line position to engage the screen by means of a hook or similar tool and to withdraw it through the opening 25.

From the foregoing description it will be evident that the removal of a screen and its replacement is a comparatively easy matter. When the linkage is in the unlatched position, the screen is entirely free from any clamping action against it. Another important advantage of my screen holder is that it tends to correct irregularities in the shape of the screen. Such screens are necessarily subjected to rather rough usage which causes dents and bends in the screens and which in many of the prior screen holders renders the screens useless until they have been laboriously hammered or rolled into correct shape. With my screen holder, however,' the space between the ribs l2 and the arms [4 in their dotted line position is so great that ordinary irregularities in the shape of the screen will not result in any binding action. The clamp is then applied and this clamp exerts sufficient pressure against the edges of the screen to correct any irregularities which are apt to develop in the screen through rough usage.

Having thus described my invention in such full, clear, and exact terms that its construction and operation will be readily understood by others skilled in the art to which it pertains, what I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a mill casing having side walls, arcuate ribs projecting inwardly from said side walls, an arcuate screen seated in contact with said ribs, a pair of arcuate arms pivotally secured to said casing in proximity to said screen and adapted for movement to clamp said screen against said ribs, a U-shaped handle member pivotally secured to said arms, a pair of rotatively adjustable disks in said side walls, and a second pair of arms pivotally secured to said handle member and eccentrically and pivotally secured to said disks, said second pair of arms and said handle member being movable into substantial alignment for forcing said arcuate arms tightly against the lateral edge portions of said screen.

2. In combination, a mill casing having side walls, arcuate ribs projecting inwardly from said side walls, an arcuate screen seated in contact with said ribs, a pair of arcuate arms having an offset pivotal axis in said mill in proximity to said screen and adapted for movement to clamp said screen against said ribs, a U-shaped handle member pivotally secured to said arms, a pair of rotatively adjustable disks in said side walls, and a second pair of arms pivotally secured to said handle member and eccentrically and pivotally secured to said disks, said second pair of arms and said handle member being movable into substantial alignment for forcing said arcuate arms tightly against the lateral edge portions of said screen.

3. In a pulverizing mill, the combination with a casing having a screen opening and a marginal seat about the opening, a screen removably fitted to the seat, and a frame for the screen, a pastcenter toggle lever clamp engaging at one end against the frame and an eccentrically adjustable pivot for the other end of the clamp for adjustment to compensate for wear and screens of various thicknesses, said toggle lever clamp adapted for initial movement to bind the frame against the screen and conform the same to said marginal seat.

4. In a pulverizing mill, the combination with a casing having a screen opening and a marginal seat about the opening, a screen removably fitted to the seat and a frame pivoted at one end to the casting adjacent one end of the opening, a toggle lever clamp pivoted at one end to the free end portion of said frame, and an eccentric pivotal mounting for the other end of said clamp to adjust the same to compensate for wear and for different thicknesses of screens, said toggle lever clamp adapted for initial operation to bend said frame against the screen and conform the latter to said seat, said toggle lever clamp adapted for final movement into past-center position to locate the frame in clamping position.

GAROLD C. J. GRAY. 

